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Quiet strength: Robert Silman on engineering the Harvard Art Museums

When the doors to the new Harvard Art Museums open this month, Renzo Piano’s dramatic cantilevered glass galleries and tent-like skylight, already partly visible from the street, will be fully revealed. Less visible, but just as dramatic, are the intricate contributions of Robert Silman Associates, the structural engineering firm that worked with Renzo Piano Building Workshop to tame challenging site and design features.

Bob Silman teaches Philosophy of Technology and Conservation of Older Buildings at the Harvard University Graduate School of Design. He established RSA nearly 50 years ago and has earned honors for his expertise in preservation, having worked on historic buildings like Carnegie Hall, Fallingwater, and the Immigration Museum at Ellis Island. This is the third collaboration between RSA and RPBW; they initially worked together on the renovation and extension of New York’s Morgan Library & Museum in 2006 and are currently collaborating on the new Whitney Museum, scheduled to open in 2015.

GSD reporter Barbara Epstein spoke with Bob Silman about his partnership with Renzo Piano and the challenges of combining new construction with historic preservation in a recent interview.

GSD: Tell me about the role of RSA in the Harvard Art Museums project and what you found especially challenging.

Robert Silman: Our focus was on executing this supremely beautifully detailed architecture, because Renzo’s strength is exquisite detailing. It’s complex and integrated, so we’ve been in it from the beginning, and the decisions are made as a team. To create the new levels we ended up digging two full stories below the original 1926 building. Keeping the building in place and not letting it fall into the hole was a very big challenge.

When you excavate next to an existing building, the danger is that you undermine that building. We used a technique called a slurry wall, where you dig a trench next to the building and fill it back up with a pudding of bentonite clay strong enough to hold up the building. Then concrete is pumped in, and it’s denser than the clay so it ultimately displaces it. The remaining concrete wall continues to function as a permanent basement wall.

The cantilevering to create the glass gallery on the north side, the Winter Garden, was also challenging. It hangs out almost 20 feet and the glass makes it seem to really float. A sliding screen, which is part of the exterior facade, controls the amount of light admitted, which is somewhat unusual.

The pièce de résistance is its spectacular glass roof, which is Renzo’s trademark. Underneath it are the conservation studios, and the spaces are wonderful. It makes you want to be a conservator.

We had to make it delicate but strong; you don’t want to see a lot of heavy structure. The main support structure for the skylight is coated with intumescent paint, which will foam and form a layer of thermal insulation to protect the steel against collapse in the event of a fire. And it goes on like paint so it leaves the shape exposed—it’s visually more appealing.

GSD: You have worked with Renzo Piano before. What made RSA the right firm for this job?

RS: We’ve developed a relationship over the last 15 years. With the Morgan Library, our first effort together, there was the need for a rare book vault and the best place was underground. Of course water is always a danger when working underground; also we were excavating rock next to the old, magnificent building. RSA had just finished Zankel Hall, excavating under Carnegie Hall while it continued to operate, and that was considered to be an engineering marvel.

I collaborated with Renzo on the important issues and ultimately on the design of the roof. The original roof design would have worked structurally, but there’s more to structure than just making it work. Renzo has always used structure as his organizing design principle, and he listened when I said I didn’t feel there was clarity in the structural system. We talked about how to make it very articulated at the small level and very bold at the big level so that somebody who has no concept of the structures at all could get the feeling about how it works. Working with him on a personal basis was really quite wonderful.

It does help that we’re sensitive to the needs of older buildings and understand how to protect them, and our work with historic buildings informs our work with new buildings as well.

GSD: What led you into engineering?

RS: I was a liberal arts student at Cornell, and though I studied architecture for one year, I graduated in political philosophy. When I got out of the army I got a job at a small construction company. I read an article in an architectural magazine noting the creative buildings being built in Europe and bemoaning the dearth of creative structural engineers in America. And I thought, I can do that. I went to NYU at night for a bachelors in civil and structural engineering and then a masters. At 30 I started my own firm. I didn’t have any clients or prospects—I had youth.

GSD: How has your practice evolved over time?

RS: In the beginning I took what I could get. I started doing historic preservation because in the 1960s there were a lot tenement renovations in the South Bronx, Bed-Stuy, and Harlem. So I learned to work in old buildings—but they were hardly historic—we eventually renovated 13,000 units of housing. The first actual historic building I worked on was Carnegie Hall, which in 1971 was dirty and dark, ill used, and threatened with being torn down.

My firm grew up with the historic preservation movement. I started in 1966, the date of the National Historic Preservation Act and the establishment of the NYC Landmark Preservation Commission. Penn Station had just been torn down and there was rebound from that that we were able to capitalize on. I never had formal training; I learned on the job.

GSD: You’ve established a legacy with some very significant buildings. Do you have a favorite?

RS: Naturally there are some dramatic projects that are a significant piece of our work, like Fallingwater. But we try to give everybody, no matter their stature, the maximum.

GSD: You’ve taught at the GSD and other architecture schools. How does it inform your work and thinking?

RS: I’m the structural studio design critic for second-year students at the GSD, so I get to work with every one of them. In my course, Conservation of Older Buildings: Techniques and Technics, we cover evaluating old buildings, the causes of deterioration, and the properties of recent and past building materials. Students become familiar with the technical issues of present day conservation theories.

I’ve invited in a diverse range of guest lecturers: architects, developers, and academics. Stephanie Meeks came from the National Trust for Historic Preservation, as did Bob Hammond, the cofounder of the Highline. They provide a breadth of experience that enlivens the conversation.

I find working with the students wonderfully gratifying; GSD faculty and students are at such a high level. And I find the level of programming at the GSD incredible. There are several things going on every day, and I want to do it all. I find myself spending much more time teaching here than I have anywhere else.